The findings come from a cohort study appearing in The Lancet Diabetes & Endocrinology, which analysed data from a previous trial looking at the effect of aspirin on risk of miscarriage in women with a history of pregnancy loss.
That study also measured vitamin D status in around 1,200 women – providing a basis for secondary analysis now of any potential link between vitamin D levels and risk.
“We did a secondary analysis of a prospective cohort from the block-randomised, double-blind, placebo-controlled EAGeR trial,” wrote the team – led by researchers at the US National Institutes of Health.
Women who had sufficient preconception vitamin D concentrations were 10% more likely to become pregnant and 15% more likely to have a live birth, compared to those with insufficient concentrations of the vitamin, the new analysis showed.
"Our findings suggest that vitamin D may play a protective role in pregnancy," commented the study's principal investigator Dr Sunni Mumford – from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), USA.
The NIH team analysed data collected as part of the Effects of Aspirin in Gestation and Reproduction (EAGeR) trial, which looked to determine if daily low-dose aspirin (81 milligrams) could prevent miscarriage in women with a history of pregnancy loss.
As part of that trial blood levels of vitamin D were tested for roughly 1,200 women before pregnancy and again at the eighth week of pregnancy.
“Women with sufficient preconception 25-hydroxyvitamin D were more likely to achieve clinical pregnancy and livebirth than were women with insufficient concentrations,” wrote the team.
Among women who became pregnant, each 10 nanogram per milliliter increase in preconception vitamin D was associated with a 12-percent lower risk of pregnancy loss, reported Mumford and colleagues.
But while pre-conception vitamin D level were significantly linked to a lowered risk of pregnancy loss, levels at eight weeks of gestation were not, they added.
The NIH team noted that since the associations were found as part of a secondary analysis it is impossible to prove any cause and effect at this point – adding that further studies are now needed to determine whether providing vitamin D to women at risk for pregnancy loss could increase their chances for pregnancy and live birth.
Source: The Lancet Diabetes & Endocrinology
Published online ahead of print, doi: 10.1016/S2213-8587
“Association of preconception serum 25-hydroxyvitamin D concentrations with livebirth and pregnancy loss: a prospective cohort study”
Authors: Mumford, SL, et al